Drive circuit and switching power supply device

A drive circuit, which is a drive circuit configured to drive a first switching element, comprising:

• a first diode, a cathode terminal of which is connected to a gate terminal of the first switching element;
• a second switching element, a first terminal of which is connected to an anode terminal of the first diode, a second terminal of which is connected to the gate terminal of the first switching element, a third terminal of which is connected to a source terminal of the first switching element;
• a third switching element, a drain terminal of which is connected to the anode terminal of the first diode, and a source terminal of which is connected to the source terminal of the first switching element;
• a parallel circuit, one end of which is connected to a cathode terminal of a Zener diode and one end of a capacitor, and the other end is connected to an anode terminal of the Zener diode and the other end of the capacitor;
• and
• a drive transformer having a coil, one end of the coil is connected to the drain terminal of the third switching element via the parallel circuit, the other end of the coil is connected to a gate terminal of the third switching element, and is connected to the source terminal of the third switching element via a second diode, wherein
• one end of the parallel circuit is connected to one end of the coil, a cathode terminal of the second diode is connected to the other end of the coil, and
• at least one of the connection between the second terminal and the gate terminal of the first switching element and the connection between the third terminal and the source terminal of the first switching element is connected via a resistor.